Without limiting the scope of the invention, its background is described in connection with recovery methods for insoluble and low solubility compounds having economic value from aqueous mixtures that may include one or more types of biological cells or cellular debris.
U.S. Pat. No. 3,956,112, issued to Lee, et al., is directed to a membrane solvent extraction. Briefly, this patent is said to describe a membrane solvent extraction system that is used to separate two substantially immiscible liquids and extract a solute through a solvent swollen membrane from one solvent liquid phase to the extracting solvent liquid without direct contact between the liquid phases. The membrane extraction method has advantages over conventional solvent extraction and may be applied as the mechanism in separation, purification, pollutant removal and recovery processes. This reference relies on liquid extraction, as the solvent swells the membrane to provide the separation.
U.S. Pat. No. 4,439,629 issued to Ruegg (1984) describes a process for extracting either or both beta-carotene or glycerine from algae containing these substances, especially from algae of the genera Dunaliella. According to the Ruegg patent either or both of beta-carotene or glycerine can be extracted from algae. If it is desired to extract beta-carotene, the algae are first treated with calcium hydroxide and then filtered. The residue from this filtration is treated with a beta-carotene solvent, which removes the beta-carotene from the residue and into the solvent. The beta-carotene can be recovered from the solvent by conventional means. If it is desired to extract glycerine, the filtrate from the treatment of the algae with calcium hydroxide is neutralized, concentrated and the residue from the solid is treated with a lower alkanol to remove glycerine from the residue.
U.S. Pat. No. 5,252,220, issued to Coughlin, et al., is directed to the preparation of analytical samples by liquid-liquid extraction using microporous hollow-fiber membranes. Briefly, this patent is said to teach a method and apparatus for accomplishing improved liquid-liquid extraction employing microporous hollow-fiber membranes. A number of possible modes of liquid-liquid extraction are possible according to the invention. As with the prior art, this patent relies on the interaction between two liquids, one of the contact side and one on the other side of the membrane for separation.
U.S. Pat. No. 5,378,639 issued to Rose et al. (1995) discloses a method for the solvent-extraction of β-carotene from an aqueous algal biomass suspension, whereby a vegetable oil which is immiscible with water is mixed with an aqueous biomass suspension, the biomass containing the β-carotene, to form a mixture of the organic phase and the aqueous suspension, whereby the β-carotene is caused to dissolve in the organic phase. This is followed by separation of the organic phase from the aqueous phase by passing the organic phase containing the dissolved β-carotene through a semi-permeable membrane to effect microfiltration or ultrafiltration of the organic phase. The membrane is of a material that is hydrophobic and the organic phase is passed through the membrane with a pressure drop across the membrane which is lower than that which causes the aqueous phase to pass through the membrane.
Finally, U.S. Pat. No. 6,436,290, issued to Glassford is directed to a method and apparatus for separating mixtures of organic and aqueous liquid phases. Briefly, this patent is said to include a method and apparatus for separating a mixture containing an aqueous liquid and an immiscible organic phase using microporous hollow fibers. Such mixtures are separated into a substantially organic-free aqueous phase and a substantially aqueous-free organic phase. The mixture is pressurized in a controlled low shear manner to minimize emulsification as it is contacted with the fibers. Productivity is said to be enhanced by separating as a third product stream, a further organic phase containing only small amounts of an aqueous phase, which for some applications can usefully be combined with the substantially aqueous-free organic phase.